Plate Steel

the following sheet lists the different types of steel available for mold plates together with a brief account of their properties and uses*

Mold steel applications





Low-carbon, also known as plain plates, carbon or mild steel

support locating rings

BS907 (EN8J AISI 1020 DIN 1.180.5

Used for economy in noncritical applications

Prehardened or pretoughened alloy too] steels

Cavities, punches and cores

BS4569 BP20 AISI P20 DIN 1.2713

Alloy tool steel used unhardened. Can be locally heat-treated

Fully hardening alloy tool steels

High volumes where high quality, strength and hardness are required for cavities and cores

BS4569 (EN30B) AISI H13 DIN 1,2.34.3

High-quality tool steel. First choice for long-running jobs

Stainless steel

Used for corrosion resistance to protect against corrosive materials such as PVC

13S (E.N57) AISI 420 SS DIN 414 SS

Stainless steels contain up to 18% chromium mu\ hence have worse heat transfer

High-carbon—high- chrome

Cavities and cores where high levels of hardness are  required

BS (EN308)


Very hard when heat treated* Used for small parts. Prone to stress cracking

Nitriding steels

Areas of high wear. Sliding surfaces, ejector pins and sleeves

BS907 722M24 AISI HI3 DIN 1.2307

Extensively used for small sliding parts

The most frequently used standard is the AISI, which stands for the American Iron and Steel Institute. By international agreement the AISI designator system has been adopted and hence literature will refer to this standard. All AISI specifications have an initial identification letter, which helps to identify steel types as shown in the following

AISI steel designations

Identification letter

Type of steel


Air hardening steels


Carbon steels


High-carbon-high- chrome steels


Carbon—tungsten steels


Hot work die steel

(H1-H19 chromium base)

(H20-H.39 tungsten base)

(H40—H49 molybdenum base)


Low alloy steels


Molybdenum base steels


Oil hardening steels


Mull steels

(PI—P19 low-carbon)

(P20—P39 other types)


Shock-resistant steels


Tungsten-base steels


Water hardening steels

The most commonly used steels for injection molding tools are as shown the following . The alloy steels list steel will machine readily (conventional machining and EDM) and will support high levels of polish. They are also suitable for texturing using EDM and photo etch techniques.

These are not the only steels used for injection mold tools but they do represent those used for the majority of applications. Specialist steels may be used for more demanding applications, e.g.” stainless steel for corrosion resistance, and high-carbon-high-chrome to achieve ultra-hard cavity inserts.

AISI designated mold steels

Type of steel



Mild Steel

MSI 1020

For backplanes, support plates, support register rings and ejector bars

Nickel Chrome Alloy

AIS] H13

Used unhardened for cavity backing plates where high loads are likely and for medium-quantity jobs for cavities and cores, or for plates likely to suffer bruising,  runner system plates and stripper plates on mutilate tools.

Used hardened for high-quality, long-running jobs for all cavities, cores and punches,

Hardness value 48-52 HRc

Nickel Chtome Alloy


Pretoughened steel used for medium-volume work. Material can be machined in this state. It is about halfway between the unhardened and hardened grades of H13 in toughness and hardness. Used for cavities and com Hardness value 28-32 HRc